1. Forey, Alan J. (1980), ‘The military Orders in the crusading proposals of the late-thirteenth and early-fourteenth centuries’, Traditio 36:
2. Schmandt, Raymond H. (1975), ‘The Fourth Crusade and the Just-War theory’, Catholic Historical Review 61:
3. Brand, Charles M. (1968a), ‘A Byzantine plan for the Fourth Crusade’, Speculum 43:
4. Abulafia, David (1988), Frederick II: a medieval emperor, London
5. Folda, Jaroslav (1965), ‘The Fourth Crusade, 1201–1203 (some reconsiderations)’, Byzantinoslavica 26: